If you don't mind not going AFK then just party them and start the bots making sure they are on the same quest. They will usually stay in sync more or less. They do get out of sync due to gathering quests where there are limited resources where one sorta follows the other around gathering resources or one is waiting for an NPC the other is getting quest from or one getting stuck somewhere or gathering. So every now and then you will need to correct and get them on the same quest.
One thing you will need to watch if they are questing in "sync" is they will both use the same pathing. It becomes evident when they both stand in the same place to get quests or buy and such that they might be bots. Something that needs to be taken care of, possibly a randomization factor.
Then again you could use Lazy raider and do manual questing with bot fighting.